type.hh

00001 // Copyright (C) 2001, 2002, 2003  EPITA Research and Development Laboratory
00002 //
00003 // This file is part of the Olena Library.  This library is free
00004 // software; you can redistribute it and/or modify it under the terms
00005 // of the GNU General Public License version 2 as published by the
00006 // Free Software Foundation.
00007 //
00008 // This library is distributed in the hope that it will be useful,
00009 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00010 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00011 // General Public License for more details.
00012 //
00013 // You should have received a copy of the GNU General Public License
00014 // along with this library; see the file COPYING.  If not, write to
00015 // the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
00016 // Boston, MA 02110-1301, USA.
00017 //
00018 // As a special exception, you may use this file as part of a free
00019 // software library without restriction.  Specifically, if other files
00020 // instantiate templates or use macros or inline functions from this
00021 // file, or you compile this file and link it with other files to
00022 // produce an executable, this file does not by itself cause the
00023 // resulting executable to be covered by the GNU General Public
00024 // License.  This exception does not however invalidate any other
00025 // reasons why the executable file might be covered by the GNU General
00026 // Public License.
00027 
00028 #ifndef NTG_CORE_TYPE_HH
00029 # define NTG_CORE_TYPE_HH
00030 
00031 /*
00032   Utility classes.
00033 */
00034 
00035 namespace ntg
00036 {
00037 
00038   // FIXME: see comments in ntg/core/value.hh about this duplicate of
00039   // metalic's code.
00040 
00041   /*-------.
00042   | any<E> |
00043   `-------*/
00044 
00046   template <class E>
00047   class any
00048   {
00049   public:
00050     typedef E exact_type;
00051     
00052     E& exact() { return static_cast<E&>(*this); }
00053     const E& exact() const { return static_cast<const E&>(*this); }
00054   };
00055 
00056   /*------------------.
00057   | any_(const_)class |
00058   `------------------*/
00059 
00060   /*
00061     Classes used to disambiguate overloading. They can store an
00062     instance of any object and restore it later.
00063   */
00064 
00065   template <class T>
00066   class any_class
00067   {
00068   public:
00069     any_class(T& t) : _target(t) {}
00070 
00071     T& exact() { return _target; }
00072 
00073   private:
00074     T& _target;
00075   };
00076 
00077   template <class T>
00078   class any_const_class
00079   {
00080   public:
00081     any_const_class(const T& t) : _target(t) {}
00082       
00083     const T& exact() const { return _target; }
00084 
00085   private:
00086     const T& _target;
00087   };
00088 
00089 } // end of ntg.
00090 
00091 #endif // !NTG_CORE_TYPE_HH

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